Boromir leaves Minas Tirith for Rivendell

'When I was sent out as a messenger, I passed through the Gap by the skirts of the White Mountains, and crossed the Isen and the Greyflood into Northerland. A long and wearisome journey. Four hundred leagues 1 I reckoned it, and it took me many months; for I lost my horse at Tharbad, at the fording of the Greyflood.' 2

The Fellowship of the Ring, LoTR Book 2, Ch 8, Farewell to Lórien

'In this evil hour I have come on an errand over many dangerous leagues to Elrond: a hundred and ten days I have journeyed all alone. But I do not seek allies in war. The might of Elrond is in wisdom not in weapons, it is said. I come to ask for counsel and the unravelling of hard words....

'Of these words we could understand little, and we spoke to our father, Denethor, Lord of Minas Tirith, wise in the lore of Gondor. This only would he say, that Imladris was of old the name among the Elves of a far northern dale, where Elrond the Halfelven dwelt, greatest of lore-masters. Therefore my brother, seeing how desperate was our need, was eager to heed the dream and seek for Imladris; but since the way was full of doubt and danger, I took the journey upon myself. Loth was my father to give me leave, and long have I wandered by roads forgotten, seeking the house of Elrond, of which many had heard, but few knew where it lay.'

2When Boromir made his great journey from Gondor to Rivendell — the courage and hardihood required is not fully recognized in the narrative — the North-South Road no longer existed except for the crumbling remains of the causeways, by which a hazardous approach to Tharbad might be achieved, only to find ruins on dwindling mounds, and a dangerous ford formed by the ruins of the bridge, impassable if the river had not been there slow and shallow — but wide.

Unfinished Tales, Part 2, Ch 4, Appendix D, The History of Galadriel and Celeborn: The Port of Lond Daer